Final answer:
ServiceNow client-side scripts execute in the user's web browser and are primarily written in JavaScript. This allows for interactive functions to be performed without constant server communication. HTML structures content, while CSS styles it, but JavaScript is what allows for script execution and interactivity.
Step-by-step explanation:
ServiceNow client-side scripts, such as Client Scripts and UI Policies, execute in the user's web browser. These scripts are primarily written in JavaScript, which is the scripting language used to add interactivity to web pages. While Jelly is a templating engine used on the server-side in ServiceNow, JavaScript runs on the client-side, enabling real-time interactions without the need to communicate with the server for every action.
HTML (HyperText Markup Language) is used to structure the content on web pages and CSS (Cascading Style Sheets) is utilized for presentation and design, but the execution of scripts that provide interactive functions in a live web page environment is done through JavaScript. This is also true in the ServiceNow platform, where JavaScript plays a crucial role in enhancing user experience with dynamic client-side functionality.